HydroClim Minnesota for Early May 2020
A monthly electronic newsletter summarizing Minnesota's climate conditions and the resulting impact on water resources. Distributed on the first Thursday of the month.
State Climatology Office - DNR Division of Ecological and Water Resources, St. Paul
distributed: May 7, 2020
What happened in April 2020:
- In general, April 2020 was cool and fairly dry across Minnesota. April was cooler than in 2019 but warmer than in 2018, and April has not been warmer than the 30-year normal since 2017. April started snowy but then turned dry, and if not for a heavy rain event in the closing days of the month, precipitation deficits would have been even higher. The statewide precipitation average was 1.23 inches, about 1.04 inches below normal.
[see: April 2020 Precipitation Total Map | April 2020 Precipitation Departure Map | April 2020 Climate Summary Table | April 2020 Percent of Normal Precipitation Map]
- The main weather event of April 2020 was the April 12 Easter snowstorm. Heavy snow fell over parts of central and southern Minnesota. The Twin Cities saw its highest Easter snowfall on record with 6.6 inches. Rochester had its 2nd highest Easter total on record with 7.5 inches. This marks the 3rd year in a row with a significant mid-April snowfall in the state.
[see: Easter Snowstorm, April 12, 2020]
- Just like in 2018 and 2019, snowfall in mid-April caused below normal temperatures. Minimum temperatures on April 15 flirted with record lows. The Twin Cities had a minimum of 19 degrees F on the 15th. The lowest temperature for April 2020 in he state was -10 degrees on April 4, near Goodridge in Pennington County. The highest temperature found was 83 degrees near Sherburn in Martin County on April 23. The statewide average temperature was 39.4 degrees, or 3.2 degrees below normal.
[see: April 2020 Climate Summary Table | 2020 April Departure from Normal Temperature Map
Where we stand now:
- Seasonal precipitation totals so far (April 1 through May 5) ranked well below the historical medians over all but the northwest part of Minnesota, where a small area was in the 70th percentile.
[see: Seasonal Precipitation, Percent Normal and Ranking Maps]
- The final snow depth map of the season was produced on April 16, as the state's snowpack dwindled. Snow depths up to 12 inches were reported on that date across the Lake Superior highlands. The Wolf Ridge Environmental Learning Center in Lake County lost its last snow cover on April 25.
[see: Snow Depth Map: April 16, 2020]
- The U. S. Drought Monitor map released on May 7 shows a small area of Abnormally Dry conditions in west central Minnesota due to short-term dryness. The U.S. Drought Monitor index is a blend of science and subjectivity where drought categories (Moderate, Severe, etc.) are based on several indicators.
[see: Drought Conditions Overview]
- The U.S. Geological Survey reports that stream discharge values are above to much above normal in the far western parts of the state, to near normal in the rest of Minnesota. There are a few pockets of below normal streamflow measurements beginning to emerge, especially in north central Minnesota.
[see: USGS Stream Flow Conditions]
- Water levels on most Minnesota lakes vary depending on lake and location in the state. The Mille Lacs lake level for early May was about a foot higher than the median. The ice left Mille Lacs on April 26, two days earlier than last year and one day later than the median. On May 6, Minnetonka was at 929.35 with 20 cfs flowing through Gray's Bay Dam. Last year at this time the lake had 250 cfs flowing out the dam. White Bear Lake was at 924.98 feet on May 7. Water has been flowing out of White Bear Lake since April 2019. Rainy Lake is slightly higher than normal for the time of year. Lake of the Woods was at its 45th percentile for May 7th, at 1058.53ft. Lake Superior was forecast to be at 602.49 feet on May 1, eleven inches higher than the monthly average for May and two inches lower than early May 2019. All the Great Lakes are well above historical averages for May.
[see: Mille Lacs Lake Water Level | Lake Minnetonka Water Level | White Bear Lake Water Level | Lake of the Woods Control Board Basin Data | Corps of Engineers Great Lakes Water Levels]
- A fairly dry April and early May assisted spring crop planting. 76% of the corn crop was planted by May 3, well ahead of the last two years. The Agricultural Statistics Service reported on May 4 that topsoil moisture supplies across Minnesota are 0 percent Very Short, 11 percent Short, 78 percent Adequate, and 17 percent Surplus.
[see: Agricultural Statistics Service Crop Progress and Condition]
- The potential for wildfires on May 7, rated by DNR Forestry as ranging from Very High over much of the north and west central to High in the east, including the Twin Cities metro area. There was even a pocket of Extreme fire danger over Carlton and southern St. Louis County. Moderate conditions are present in southwest and south central Minnesota.
[see: Fire Danger Rating Map]
- Lake ice out started out being a week to ten days ahead of the median across southern Minnesota. Then cooler weather arrived and lake ice out progress slowed a bit to be a day or two either side of the median across central and northern Minnesota. By May 7, the only remaining lakes with partial ice over were a few lakes in northern Cook County.
[see: 2020 Lake Ice-Out Dates | DNR Conservation Officer Reports]
- The May precipitation outlook has a tendency for below normal precipitation for all but the northwest corner of the state. May precipitation normals range from just over two inches in northwest Minnesota to just less than four inches in southeastern counties. The historical probability of measurable precipitation for any given day in May ranges from 25 percent in the northwest to near 40 percent in the southeast.
[see: Climate Prediction Center 30-day Outlook | May Precipitation Normal Map]
- The outlook for May calls for a equal chances for above, below and normal temperatures across the state, except in the far northeast tip, where there is a slight tilt for below normal temperatures. Normal May high temperatures are in the low to mid-60s early in the month, rising to the low to mid-70s at month's end. Normal May low temperatures are in the mid-30s to near 40 to start the month, and climb to the mid-40s to low 50s as the month ends.
[see: Climate Prediction Center 30-day Outlook | May Temperature Normal Map]
- The 90-day precipitation outlook for May through July indicates a tendency greater-than-equal for above normal precipitation for central and especially southern Minnesota, with equal chances of below-normal, near-normal, or above-normal conditions for northern Minnesota, The May through July temperature projection shows a broad area covering much of the region with equal chances of below-normal, near-normal, or above-normal conditions.
[see: Climate Prediction Center 90-day Outlook]
- The National Weather Service produces long-range probabilistic river stage and discharge outlooks for the Red River, Minnesota River, and Mississippi River basins. These products address both high flow and low flow probabilities.
[see: National Weather Service - North Central River Forecast Center]
From the author:
- Signs of spring continue across the state. [see: Spring Phenology]
Upcoming dates of note:
- May 21: National Weather Service releases 30/90 day temperature and precipitation outlooks
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Pete Boulay, DNR Climatologist